The wings are airfoils attached to each side of the fuselage and are
the main lifting surfaces which support the airplane in flight. There are
numerous wing designs, sizes, and shapes used by the various manufacturers.
Each fulfill a certain need with respect to performance expected for the
particular airplane. How the wing produces lift is explained in subsequent
chapters.

Wings are of two main types - cantilever and semicantilever (Fig.
2-3). The cantilever wing requires no external bracing; the stress
is carried by internal wing spars, ribs, and stringers. Generally, in this
type wing the "skin" or metal wing covering is constructed to carry much
of the wing stresses. Airplanes with wings so stressed are called stressed
skin types. Treated aluminum alloy is most commonly used as the wing covering
(Fig. 2-4). The semicantilever wing is braced both
externally by means of wing struts attached to the fuselage, and internally
by spars and ribs.

The principal structural parts of the wing are spars, ribs, and stringers.
These are reinforced by trusses, I beams, tubing, or other appropriate
devices. The wing ribs actually determine the shape and thickness of the
wing (airfoil). In most modern airplanes, the fuel tanks are either an
integral pat of the wing's structure, or consist of flexible containers
mounted inside of the wing structure.